1. Field
The present disclosure relates to techniques for communicating optical signals. More specifically, the present disclosure relates to an optical source that uses feedback to maintain a substantially fixed spacing between adjacent wavelengths produced by the optical source.
2. Related Art
Silicon photonics is a promising technology that can provide large communication bandwidth, low latency and low power consumption for inter-chip and intra-chip connections. In the last few years, significant progress has been made in developing low-cost components for use in inter-chip and intra-chip silicon-photonic connections, including: high-bandwidth efficient silicon modulators, low-loss optical waveguides, wavelength-division-multiplexing (WDM) components, and high-speed CMOS optical-waveguide photodetectors. However, a suitable low-cost WDM optical source, such as a multi-wavelength laser source, remains a challenge and, in its absence, poses an obstacle to implementing WDM silicon-photonic links.
In particular, traditional WDM links operate on a predefined wavelength grid with fixed channel spacing, such as that specified by International Telecommunication Union (ITU) standard, ITU-T G.694.1. As a consequence, existing WDM optical sources, such as lasers, used in these traditional WDM links are tuned and locked to the predefined wavelength grid. However, wavelength control for such existing WDM optical sources is typically quite complicated. For example, air-gap etalon filters are often used in the existing WDM optical sources to implement wavelength locking These air-gap etalon filters are usually bulky, and therefore are not suitable for integration or for use in WDM silicon-photonic links in which there may be thousands of integrated WDM optical sources.
Hence, what is needed is an optical source without the above-described problems.